This invention relates to a method of making a stencil and a method of applying a marking to a surface by the use of a stencil, particularly a stencil having the precision cutting and chemical composition required for etching glass.
Vehicle identification numbers are sometimes etched into the glass windows of the vehicle. Such an arrangement is desirable in that the markings are permanent, yet unobtrusive.
U.S. Pat. No. 4,585,514 - Scallan and U.S. Pat. No. 4,781,792 - Hogan, disclose systems for etching glass wherein a stencil template is cut with an electric typewriter and subsequently adhered to glass by the use of a wetting technique. An etching compound is then applied to the stencil for a period of time, following which the stencil is removed and the window wiped clean. In the wetting technique, the cut stencil is displaced or otherwise wet with water or a solvent. The glass area to be etched is thoroughly cleaned and the area moistened prior to the application of the stencil to the surface to be etched. The stencil is held in place by capillary action. However, any mixing of the residual wetting agent and the etching compound may produce an incomplete etching action on the surface of the material to be etched due to a dilution of the etching compound, thereby requiring that the stencil and surrounding area be carefully blotted to be free of exposed wetting agent prior to etching compound application.
A stencil cut with an electric typewriter has also been applied to glass with an adhesive. The stencil material is furnished with adhesive applied to its backside and covered by a backing strip. The stencil is then "cut" with the electric typewriter, which does not penetrate the backing strip. The backing strip is removed when the stencil is to be applied to the glass. While this approach is convenient for application to the glass, the cut provided by the typewriter is not sharp and clear. A primary reason for this is that the stencil material removed or displaced by the typewriter key is relatively fibrous, and hence leaves a rather fuzzy line, rather than a sharp one. Similarly, the adhesive material is not completely removed in a sharp well-defined line, being only pushed aside or partially removed. Such adhesive material remaining in the area desired to be etched interferes with the etching compound.
Another disadvantage of the stencil material that will be "cut" by the typewriter key is that it is somewhat delicate such that it requires care and skill in handling and positioning it on the glass after removal of the backing strip. Repositioning is particularly difficult if that should be necessary to obtain proper alignment on the glass. Letters requiring an unsupported free end, such as the pair of horizontal fingers needed in framing a capital "E", may become blurred as a result of the misalignment of the unsupported fingerlike tips.
U.S. Pat. No. 4,316,766 discloses a stencil for etching glass wherein the stencil is cut by electrostatic means, and adhesive is then applied to the back of the stencil to attach it to the surface to be marked.
A need exists for an improved stencil and stencil forming method, as well as a method for utilizing a stencil produced by such a method for etching glass or in conjunction with other types of stenciling operations.
It is therefore an object of the present invention to provide a method of cutting stencil templates using non-mechanical means to produce a consistent, repeatable cut with a degree of preciseness heretofore unachieved in the art.
Another object of the present invention is to produce a stencil template which is directly adherable to the surface to be etched, and is capable to maintain readily its shape when being handled and positioned or repositioned on the surface to be etched.